Spread spectrum communication synchronization acquisition decoding apparatus

ABSTRACT

According to a spread spectrum communication synchronization acquisition demodulating apparatus which can acquire synchronization timing and immediately track variation of the synchronization timing irrespective of lots of noise, in a synchronizing circuit 100, a reception signal form an antenna is converted to a base band signal in a local oscillator 1 and an LPF 2, and sampled in S/H 3. In a correlator 4, the spreading code of the reception signal is multiplied by the symbol thereof to obtain a correlation value. In a symbol integrator 5, the correlation value is demodulated on the basis of the theoretical value of the symbol corresponding to the correlation value or the judgment value after demodulation, and integrated over plural symbols to obtain a power value. In a demodulation path selection unit 8, the power value from a short-time integration path search unit 6 is integrated for a short time to select higher power values in the magnification order, and the power value from a long-time integration path search unit 7 is integrated for a long time to select higher power values in the magnification order. The reception timing is selected from the power values selected in the short-time and long-time integration path search units, and the despreading is performed according to the reception timing in the correlator 9, and a composite signal is identified in a RAKE/SD unit 11 to obtain a judgment value.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spread spectrum communicationsynchronization acquisition decoding apparatus which is mainly used at areception portion of a radio communication apparatus for spread spectrum(SS) communication, and performs synchronization acquisition andsynchronization tracking of received signals and spreading codes in adirect sequence (DS) type spread spectrum communication.

2. Description of the Related Art

A direct sequence (DS) type spread spectrum (SS) communication has beenmore increasingly studied and developed in a cellular mobilecommunication field of car phones, etc. because of little interferencebetween cellular phones and a large communication capacity.

A mobile radio communication is bidirectionally performed between a basestation having a transmitter and a receiver and a mobile unit having atransmitter and a receiver by setting a radio channel between the basestation and the mobile unit.

In this case, the transmitter basically performs digital modulation(primary modulation) such as QPSK, QAM, PSK or FSK modulation or thelike on data such as audio data, image data, program data or the likewhich are digitized, generates a spreading code such as a pseudo noisesignal (PN code) or the like in a spreading code generator, and thenmultiplies the digitally-modulated (primary-modulated) data (informationsignal) by the PN code thus generated to perform a spread spectrummodulation (secondary modulation). Further, thespread-spectrum-modulated (secondary-modulated) data is subjected to aphase modulation with predetermined carrier, and transmitted as a spreadspectrum (SS) signal from an antenna.

On the other hand, the receiver basically receives the spread spectrum(SS) signal by an antenna, and converts it to an intermediate frequencysignal or a base band signal. Thereafter, the synchronization of thespreading code used in the spreading code generator of the transmitteris acquired in a synchronizing circuit, and the same spreading code asthe transmitter is transmitted to an despreading decoder. In thedespreading decoder, the spread spectrum (SS) signal and the spreadingcode from the synchronizing circuit are multiplied to perform andespread demodulation, and finally the data are demodulated in aninformation demodulator. In the synchronizing circuit of the receiver,it is required to search a point which is coincident in phase with thetransmitted spreading code and limit the timing of the phase-coincidencepoint in a predetermined range in order to acquire and keep thesynchronization.

FIG. 3 is a block diagram showing the basic construction of asynchronizing circuit which is used in a receiver for the conventionalspread spectrum (SS) communication.

In the synchronizing circuit, a received spread spectrum (SS) signal isconverted to a base band signal by a local oscillator 1, a mixer 12 anda low pass filter (LPF) 2 which are prepared at the reception side, thenthe base band signal is sampled by a sample hold circuit 3 to obtain asampled signal, and then the sample signal is transmitted to acorrelator 4 which comprises a matched filter. The correlator 4multiplies one period of the spreading code of the received spreadspectrum (SS) signal and one period of a pre-prepared spreading codeevery chip, calculate the sum thereof and transmits the sum result to asynchronization detector 10. Here, the local oscillator 1, the mixer 12multiplying the received signal and a local oscillated frequency signaland the low pass filter (LPF) 2 acts as a signal converter forconverting the received signal to the base band signal.

FIG. 4 is a schematic diagram showing the basic construction of thecorrelator 4. The correlator 4 successively stores the spread spectrum(SS) signal converted to the base band signal into a shift register 4aevery chip, and also it generates a spreading code sequence by acoefficient generator 4b and multiplies the spreading code sequence by acoefficient generator 4b and the spread spectrum (SS) signal stored inthe shift register 4a every chip by a multiplier 4d. The multiplicationresult is transmitted to an adder 4c to calculate the sum of themultiplication result and output the sum result. When the spreading codesequence from the coefficient generator 4b and the spreading code of thereceived spread spectrum (SS) signal are coincident with each other intiming, the output of the adder 4c becomes maximum (matched pulse). Thismatched pulse is detected by the synchronization detector 10, and thedespread demodulation is performed by using the above synchronizationinformation.

In the case of the synchronizing circuit for the spread spectrum (SS)communication receiver as described above, if there are a lot of noise,an erroneous judgment of the synchronization position would occur morefrequently. Therefore, in order to take a countermeasure to the noise,the output of the matched filter is added and summed up by the amountcorresponding to several symbols, and then integrated over plural slots.However, the synchronizing circuit has another problem that when thesynchronizing timing varies, it cannot immediately follow the variationif the integration time is long.

SUMMARY OF THE INVENTION

The present invention has been implemented to solve the above problem,and has an object to provide a spread spectrum communicationsynchronization acquisition demodulating apparatus in which a propersynchronization timing can be acquired with suppressing the erroneousjudgment of the synchronization position in spite of a lot of noise, andalso even when the synchronization timing varies, the variation of thesynchronizing timing can be immediately tracked.

According to the present invention, a spread spectrum communicationsynchronization acquisition demodulating apparatus of a spreading codesynchronizing circuit provided in a radio communication apparatus forperforming a data communication in which when a spread spectrum signalwhich is obtained by modulating transmission data and subjecting themodulated data to spread spectrum processing using a spreading code andthen transmitted from a transmission side is demodulated as a receptionsignal to reproduce reception data at a reception side, the spreadspectrum signal is subjected to despread spectrum processing using thesame spreading code as the transmission side and then demodulated at thereception side, comprises: a signal converter for converting thereception signal to a base band signal; a sample hold circuit forsampling the base band signal, holding the sampled base band signal andoutputting the sampling signal; a first demodulation correlator forcorrelating the sampling signal and the spread signal based on thespreading code to obtain a first correlation value; a symbol integratorfor demodulating the first correlation value on the basis of any one ofa theoretical value of a symbol corresponding to the first correlationvalue when the symbol is known or a judgment value after demodulationwhen the symbol is unknown and integrating the demodulation result overplural symbols to calculate the power of the integration of the pluralsymbols, thereby obtaining a power value; a short-time integration pathsearch unit for adding power values over plural slots (i.e., integratingthe power value for the integration time corresponding to the pluralslots) and selecting higher power values, the number thereofcorresponding to the number of the first correlators, in themagnification order of the power per slot from a larger power per slotto a lower power per slot; a long-time integration path search unit foradding power values over plural slots whose number is larger by pluralslots than that of the short-time integration path search unit (i.e.,integrating the power value for an integration time longer than that ofthe short-time integration path search unit by the time corresponding toplural slots) and selecting higher power values, the number thereofcorresponding to the number of the first correlators, in themagnification order of power per slot from a larger power value to alower power value; a demodulation path selection unit for selecting areception timing for demodulation from the timings of the power valuesselected in the short-time and long-time integration path search unitsin the order of the magnification of power per slot; a second correlatorfor correlating the reception signal and the spread signal on the basisof the reception timing for demodulation to obtain a second correlationvalue; a detector for detecting the second correlation value andoutputting a detection signal; and a signal composite unit foroutputting a judgment value on the basis of a composite signal which isobtained by transmitting the detection signal to a RAKE/SD (SpaceDiversity) unit through the corresponding path to perform any one ofRAKE synthesis and space diversity (SD) synthesis.

In the spread spectrum communication synchronization acquisitiondemodulating apparatus, it is preferable that in the symbol integratorthe correlation value is demodulated on the basis of the theoreticalvalue of the symbol corresponding to plural slots whose number exceeds 1or the judgment value thereof, or in the symbol integrator the firstcorrelation value is demodulated on the basis of the theoretical valueof the symbol corresponding to each of plural parts to which a slot isdivided, or the judgment value thereof, the demodulation result isintegrated over plural symbols to calculate the power of the integrationof the plural symbols, and then the power values of the plural parts areadded to determine the power of the slot concerned.

Further, according to the present invention, a spread spectrumcommunication synchronization acquisition demodulating apparatus of aspreading code synchronizing circuit provided in a radio communicationapparatus in which when a spread spectrum signal transmitted from atransmission side while subjected to spread spectrum processing with aspreading code after transmission data are modulated is subjected toreception demodulation as a reception signal to reproduce the receptiondata at a reception side, the spread spectrum signal is subjected todespread spectrum processing with the same spreading code as thetransmission side and then demodulated at the reception side, comprisesa signal converter for converting a received signal to a base bandsignal with a spreading code set as one symbol period; a sample holdcircuit for sampling the base band signal, holding the sampling signaland outputting the sampling signal; a symbol integrator for demodulatingthe sampling signal on the basis of the theoretical value of a symbolwhen the symbol is known or a judgment value after demodulation for anunknown symbol, integrating the demodulation result over plural symbolsto obtain a symbol integration value; a first correlator for correlatingthe symbol integration value and the spread signal based on thespreading code to determine the power of the correlation and obtain apower value; a short-time integration path search unit for adding powervalues of plural slots and selecting higher power values in themagnification order of power per slot from a larger power value to alower power value by the number of the first correlators; a long-timeintegration path search unit for adding power values of plural slotswhose number corresponds to the time longer than that of the short-timeintegration path search unit by the time corresponding to plural slotsand selecting higher power values in the magnification order of powerper slot from a higher power value to a lower power value by the numberof the first correlators; a demodulation path selection unit forselecting a reception timing for demodulation from the timings of thepower values which are selected by excluding the same timing andadjacent timings thereto in the short-time and long-time integrationpath search units in the magnification order of power per slot; a secondcorrelator for correlating the reception signal and the spread signal onthe basis of the reception timing for demodulation to obtain a secondcorrelation value; a detector for detecting the correlation value andoutputting a detection signal; and a signal composite unit foroutputting a judgment value on the basis of a composite signal which isobtained by transmitting the detection signal to a RAKE/SD (SpaceDiversity) unit through the corresponding path to perform any one ofRAKE synthesis and space diversity (SD) synthesis.

In the above-described spread spectrum communication synchronizationacquisition demodulating apparatus, it is preferable that in the symbolintegrator the sampling signal is demodulated on the basis of thetheoretical of the symbol corresponding to the sample value of pluralslots whose number exceeds 1 as the sampling signal, or a judgmentvalue.

According to the present invention, in any one spread spectrumcommunication synchronization acquisition demodulating apparatus, thereare obtained a spread spectrum communication synchronization acquisitiondemodulating apparatus in which the power per slot which corresponds tothe timing selected in a short-time integration path search unit and ismultiplied by a weight real number α is compared with the power per slotwhich corresponds to the timing selected in a long-time integration pathsearch unit in a demodulation path selector, the same and adjacenttimings are excluded, and the reception timings for demodulation areselected in the order of magnitude, a spread spectrum communicationsynchronization acquisition demodulating apparatus in which the weightreal number α is set to a large value when a signal interference ratio(SIR) is large and set to a small value when the signal interferenceratio is small, and in a demodulation path selector, the power per slotwhich corresponds to the timing selected in a short-time integrationpath search unit and is multiplied by a weight real number α is comparedwith the power per slot which corresponds to the timing selected in along-time integration path search unit, the same timing and adjacenttimings thereto are excluded, and the reception timings for demodulationare selected in the order of magnitude, or a spread spectrumcommunication synchronization acquisition demodulating apparatus inwhich in a demodulation path selector a specific predetermined number oftimings which are selected in the magnitude order of the power per slotwhich corresponds to the timing selected in a short-time integrationpath search unit is compared with a specific predetermined number oftimings which are selected in the magnitude order of the power per slotwhich corresponds to the timing selected in a long-time integration pathsearch unit, and the same timing and adjacent timings thereto areexcluded to select reception timings for demodulation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the basic construction of a receptionunit which is a main part of a spread spectrum communicationsynchronization acquisition demodulating apparatus according to a firstembodiment of the present invention;

FIG. 2 is a block diagram showing the basic construction of a receptionunit which is a main part of a spread spectrum communicationsynchronization acquisition demodulating apparatus according to a secondembodiment of the present invention;

FIG. 3 is a block diagram showing the basic construction of asynchronizing circuit used in a conventional spread spectrumcommunication receiver; and

FIG. 4 is a schematic diagram showing a correlator having a matchedfilter structure which is provided to the synchronizing circuit shown inFIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments in which the present invention is applied to aspread spectrum communication synchronization acquisition apparatus willbe described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the basic construction of a receptionunit which is a main part of a spread spectrum communicationsynchronization acquisition demodulating apparatus according to a firstembodiment of the present invention.

The spread spectrum communication synchronization acquisition apparatusof this embodiment is provided to a radio communication apparatus inwhich when a spread spectrum (SS) signal which is subjected to spreadspectrum (SS) processing with a spreading code after transmission dataare modulated in a transmission unit is received and demodulated as areception signal in a reception unit to reproduce reception data, thedata are despread with the same spreading code and then demodulated.

Therefore, a spreading code synchronization circuit which is provided tothe reception unit is provided with plural synchronizing circuit eachcomprising a local oscillator 1 and a low pass filter (LPF) 2 whichserve as a signal converting and generating unit for converting areception signal from an antenna receiving a spread spectrum (SS) signalto a base band signal, a sample hold circuit (S/H) 3 for sampling andholding the base band signal and outputting the sampling signal, a firstcorrelator 4 for demodulation for correlating the sampling signal andthe spread signal based on the spreading code to obtain a firstcorrelation value, and a symbol integrator 5 for demodulating the firstcorrelation value on the basis of a theoretical value of the symbolcorresponding to the first correlation value or a judgment value afterdemodulation for an unknown symbol to perform plural-symbol addition,and determining the power of the plural-symbol addition, therebyobtaining a power value.

Further, the spreading code synchronizing circuit comprises a short-timeintegration path search unit 6 for adding power values over plural slotsand selecting timings in the magnification order of the power per slotfrom the timing providing the power value having the largest power perslot by the number of the first correlators 4, a long-time integrationpath search unit 7 for adding power values for a longer time than thatof the short-time integration path search unit by the time correspondingto plural slots and selecting timings in the magnification order of thepower per slot from the timing providing the power value having thelargest power per slot by the number of the first correlators 4; ademodulation path selection unit 8 for selecting a reception timing fordemodulation from the timings selected in the short-time and long-timeintegration path search units 6 and 7 in the magnification order of thepower per slot, a second correlator 9 for correlating the receptionsignal and the spread signal on the basis of the reception timing fordemodulation to obtain a second correlation value, a detector 10 fordetecting the second correlation value and outputting a detectionsignal, and a RAKE/SD unit 11 serving as a signal composite unit foroutputting a judgment value on the basis of a composite signal which isobtained by subjecting the detection signal to RAKE synthesis and SpaceDiversity (SD) synthesis through the corresponding paths.

That is, according to the spreading code synchronizing circuit, in thesynchronizing circuit 100, the reception signal which is the spreadspectrum (SS) signal received by the antenna is converted to a base bandsignal by the local oscillator 1 and the low pass filter (LPF) 2, andthen this signal is sampled every 1/2 chip in the sample hold circuit(S/H) 3 and transmitted through a memory to the first correlator 4. Thefirst correlator 4 comprises a matched filter. In the first correlator4, the reception signal which is taken out from the memory and whoseamount corresponds to one symbol of the spreading code (sampled data thesampling point of which is deviated by 1/2 chip are taken out from thememory, and it is set as one period of the spreading code of thereception signal) is multiplied by a predetermined one symbol of thespreading code (one period of the spreading code) every chip, and thesum of the multiplied values is calculated and output as a symbol signalrepresenting the first correlation value. As an example, it is repeatedat 32 times at the period of the spreading code, for example, aspreading ratio of 16 (in the case where the period of the spreadingcode is equal to 16 chips) at an interval of 1/2 chip.

However, in the first correlator 4, when the number of chips of theperiod of the spreading code is larger than the number of chips in thesearch range like a case where a long code is used, the repetition ismade at the times corresponding to the number of chips which are desiredto be searched, that is, at 100 times when the number of chips to besearched is equal to 50. Further, in the first correlator 4, when thechip interval of the chips for which the search is required is smallerthan 1/2 chip, for example, it is equal to 1/4 chip, the symbol signalthereof is interpolated by an FIR low pass interpolating filter toprepare a symbol signal every despreading timing 1/4 chip.

In the symbol integrator 5, for known symbols for which the informationof transmission signal is known, that is, pilot symbols, etc. which areknown in a transmission system, the symbol signal which is despread atan interval of 1/4 chip is demodulated on the basis of the theoreticalvalue thereof. On the other hand, for unknown symbols, the symbol signalis demodulated on the basis of a judgment value which is obtained on thebasis of a judgement after demodulation. Thereafter, the integration ismade over plural symbols to perform a plural-symbol integration. Thesymbol integration is performed over all the symbols of a slot or somesymbols of the slot, and the square of I components of the integratedsymbol signal and the square of Q components of the integrated symbolsignal are added to calculate the power value thereof and then transmitit to the short-time integration path search unit 6 and the long-timeintegration path search unit 7. In the short-time integration pathsearch unit 6 and the long-time integration path search unit 7, thepower value thus transmitted is added (integrated) over one or moreslots to perform an inter-slot integration.

For example, in the short-time integration path search unit 6, thispower value is integrated over 16 slots, four higher power values areselected, and the timing thereof and the average power per slot aretransmitted to the demodulation path selection unit 8. Further, in thelong-time integration path search unit 7, the integration of the powervalue is performed for a longer than that of the short-time integrationpath search unit 6, for example, the power value is integrated over 416slots, and then four higher power values are selected to transmit thetiming thereof and the average power per slot to the demodulation pathselection unit 8.

The difference between the short-time integration path search unit 6 andthe long-time integration path search unit 7 resides in the number ofslots over which the integration is performed. That is, the integrationslot number of the short-time integration path search unit 6 is set tobe smaller than the integration slot number of the long-time integrationsearch unit 7.

In the case where the slot length is short, the symbol integrator 5 mayperform the symbol integration over n slots (n represents an integer of2 or more), then determine the power value and then transmits the powervalue to the short-time integration power search unit 6 and thelong-time integration path search unit 7 every n slots. Conversely, inthe case where the slot length is long, the symbol integrator 5 maydivide one slot into m parts (m represents an integer of 2 or more),perform the symbol integration every part, calculate the power of thesymbol integration result over the m parts, calculate the average powerof the slot and then transmit the power value to the short-timeintegration path search unit 6 and the long-time integration path searchunit 7. At any rate, in the short-time integration power search unit 6and the long-time integration path search unit 7, theinterslot-integrated signals whose power is above a specific level orsome of then are selected to perform a preliminary selection of pathsand the average power per slot is transmitted to the demodulation pathselection unit 8 at the timing thereof.

In the demodulation path selection unit 8, a demodulation path forallocating a finger is finally selected from the path timing notifiedfrom the short-time integration path search unit 6 and the long-timeintegration path search unit 7 every antenna by referring to the averagepower per slot, and after the selection, the path timing (which is thereception timing for demodulation, and regarded as demodulation path)based on the selected antenna number and code phase is notified to thesecond correlator 9.

As the selection method are used a method of allocating the demodulationpath from all the timings in the magnification order of the averagepower per slot, a method of multiplying the power from the short-timeintegration path search unit 6 by a weight real number α with the weightreal number a set as a fixed value and then allocating the demodulationpath in the magnification order of the power, a method of multiplyingthe power from the short-time integration path search unit 6 by a weightreal number α while the weight real number α is varied in accordancewith a signal interference ratio (SIR), that is, the weight real numberα is set to a small value when the signal interference ratio is smallwhile the weight real number a is set to a large value when the signalinterference ratio is large, and then allocating the demodulation pathin the magnification order of the power, a method of allocating thedemodulation paths in a fixed manner, for example, allocatingdemodulation paths of i from the short-time integration path search unit6 and demodulation paths of j from the long-time integration path searchunit 7 (i≠j), etc. In any method, it is inhibited to select two timingscontaining the same timing or an adjacent timing thereto.

In the second correlator 9, the reception signal from the antennacorresponding to the antenna number is despread at the notified timing,and the correlation signal representing the second correlation value istransmitted to the detector 10. In the detector 10, the detection signalobtained by detecting the correlation signal is transmitted to theRAKE/SD unit 11, and the RAKE synthesis and the SD synthesis areperformed in the RAKE/SD unit 11 to obtain a composite signal.Thereafter, the composite signal is identified, and it is notified as ajudgment value to the short-time integration path search unit 6 and thelong-time integration path search unit 7.

FIG. 2 is a block diagram showing the basic construction of thereception unit which is the main part of the spread spectrumcommunication synchronization acquisition demodulating apparatusaccording to a second embodiment of the present invention.

The spread spectrum communication synchronization acquisitiondemodulating apparatus includes a synchronizing circuit 200 comprising alocal oscillation 1 and a low pass filter (LPF) 2 which serve as asignal converter for converting a reception signal to a base band signalwith a spreading code set as one symbol period, a sample hold circuit(S/H) 3 for sampling and holding the base band signal and outputting thesampling signal, a symbol integrator 5' for demodulating the samplingsignal on the basis of a theoretical value of a symbol or a judgmentvalue after demodulation for an unknown symbol, and adding pluralsymbols to calculate a symbol integration value, and a first correlator4' for correlating the symbol integration value and the spread signalbased on the spreading code to determine the power of the correlationand obtain the power value, in place of the synchronizing circuit 100 ofthe embodiment 1.

The spread spectrum communication synchronization acquisitiondemodulating apparatus is provided with a short-time integration pathsearch unit 6 for adding power values of plural slots (i.e., forintegrating the power value for the integration time corresponding tothe plural slots) and select higher power values in the magnificationorder of power per slot from a larger power value to a lower power valueby the number of the first correlators 4', a long time integration pathsearch unit 7 for integrating the power value for an integration timelonger than that of the short-time integration path search unit 6 by thetime corresponding to plural slots and selecting higher power values inthe magnification order of power per slot from a higher power value to alower power value by the number of the first correlators 4', ademodulation path selection unit 8 for selecting reception timings fordemodulation in the magnification order of power per slot from timingswhich are selected by excluding the same timing and adjacent timingsthereto in the short-time integration path search unit 6 and thelong-time integration path search unit 7, a second correlator 9 forcorrelating the reception signal and the spread signal at the receptiontiming for demodulation to obtain a correlation value, a detector 10 fordetecting a correlation value and outputting a detection signal, and aRAKE/SD unit 11 serving as a signal synthesizing unit for outputting ajudgment value on the basis of a composite signal which is obtained bysubjecting the detection signal to the RAKE synthesis and the spacediversity (SD) synthesis.

That is, in the spreading code synchronization circuit, the period ofthe spreading code is set as one symbol. First, in the synchronizingcircuit 200, the reception signal which is a spread spectrum (SS) signalreceived by the antenna is received by the antenna and converted to abase band signal in the local oscillator 1 and the low pass filter (LPS)2. Thereafter, the base band signal is sampled every 1/2 chip in thesample hold circuit (S/H) 3. In the symbol integrator 5', the sampledata of every symbol in the sampling signal at the 1/2-chip interval areused. The data are demodulated on the basis of the theoretical values ofpilot symbols which are inserted at fixed positions of the slot by thenumber of symbols which are desired to be integrated, or a judgmentvalue after demodulation when the symbol is unknown, and the integrationthereof is made over plural symbols to obtain a symbol integrationvalue. This process is also carried out at other sampling points whichare deviated by 0.5 chip, 1 chip, 1.5 chip . . . .

In the correlator 4', the symbol integration value which is obtained bythe demodulation and the integration is multiplied by one symbol of thespreading code every chip, and the sum of the multiplication iscorrelated to determine the power of the correlation and calculate thepower value. As an example, this operation is repeated at (the spreadingratio x the number of symbols to be searched) at 1/2 chip interval, forexample, at 256 times for symbols having a spreading ratio of 16 and asearch range of 8.

However, in the first correlator 4', when the interval of chips to besearched is smaller than 1/2 chip, for example, when it is set to 1/4chip, the symbol signal thereof is interpolated through the FIR low passinterpolating filter to form a symbol signal every despreading timing1/4 chip, finally the square value of I components and the square valueof Q components are added to calculate the power value, and then thecalculation result is transmitted to the short-time integration pathsearch unit 6 and the long-time integration path search unit 7. In theshort-time integration path search unit 6 and the long-time path searchunit 7, the power value is integrated over one or more slots, therebyperforming the inter-slot integration.

For example, in the short-time integration path search unit 6, the powervalue is integrated over 16 slots, four higher power values areselected, and the timing and the corresponding average power per slotare transmitted to the demodulation path selection unit 8. In thelong-time integration path search unit 7, the integration time is set tobe longer than that of the short-time integration path search unit 6.For example, the power value is integrated over 416 slots, four higherpower values are selected, and the timing and the corresponding averagepower per slot are transmitted to the demodulation path selection unit8.

In the demodulation path selection unit 8, every two reception timingsfor demodulation and every two antenna numbers based on the code phasenotified from the short-time integration path search unit 6 and thelong-time integration path search unit 7 every antenna are selected andtransmitted to the second correlator 9. However, when the totally fourreception timings for demodulation contain the same timing or adjacenttimings thereto, by referring to the average power per slot, thereception timing for demodulation and the antenna number whichcorrespond to the larger average power per slot are added.

In the correlator 9, the reception signal from the antenna correspondingto the antenna number is despread at the notified reception timing fordemodulation, and the correlation signal representing the correlationvalue is transmitted to the detector 10. In the detector 10, thedetection signal obtained by detecting the correlation signal istransmitted to the RAKE/SD unit 11. In the RAKE/SD unit 11, the RAKEsynthesis and the SD synthesis are performed to obtain the compositesignal, and then the composite signal is identified and then transmittedas a judgment value to the short-time integration path search unit 6 andthe long-time integration path search unit 7.

In the first and second embodiments, the RAKE/SD unit 11 serving as thesignal synthesizing unit is designed to perform the RAKE synthesis andthe space diversity (SD) synthesis to obtain the composite signal forobtaining the judgment value. However, in place of this function, theremay be set the function of performing only any one of the RAKE synthesisand the space diversity (SD) synthesis to obtain the composite signalfor obtaining the judgement value.

As described above, according to the spread spectrum communicationsynchronization acquisition demodulating apparatus, the proper pathsearch on the track to the high-speed path variation and the track tothe path which exists stationarily for a long time can be performedwithout lack. Therefore, the error judgment on the synchronizationposition can be suppressed, and thus the synchronization timing can beproperly acquired. In addition, even when the synchronization timingvaries, the tracking can be immediately performed, so that receptionquality can be enhanced. Further, even when the short-time integrationpath search cannot be tracked to the optimum timing due to lots ofnoise, the long-time integration path search tracks the receptiontiming, and thus the reception can be stably performed. In addition, thetransmission side is not required to have a strong transmission outputin order to constant reception quality, so that the interference can besuppressed.

Although the present invention has been shown and described with respectto best mode embodiments thereof, it should be understood by thoseskilled in the art that the foregoing and various other changes,omissions, and additions in the form and detail thereof may be madetherein without departing from the spirit and scope of the presentinvention.

What is claimed is:
 1. A spread spectrum communication synchronizationacquisition demodulating apparatus of a spreading code synchronizingcircuit provided in a radio communication apparatus for performing adata communication in which when a spread spectrum signal which isobtained by modulating transmission data and subjecting the modulateddata to spread spectrum processing using a spreading code and thentransmitted from a transmission side is demodulated as a receptionsignal to reproduce reception data at a reception side, the spreadspectrum signal is subjected to despread spectrum processing using thesame spreading code as the transmission side and then demodulated at thereception side, comprising:a signal converter for converting thereception signal to a base band signal; a sample hold circuit forsampling the base band signal, holding the sampled base band signal andoutputting the sampling signal; a first demodulation correlator forcorrelating the sampling signal and the spread signal based on thespreading code to obtain a first correlation value; a symbol integratorfor demodulating the first correlation value on the basis of any one ofa theoretical value of a symbol corresponding to the first correlationvalue when the symbol is known or a judgment value after demodulationwhen the symbol is unknown and integrating the demodulation result overplural symbols to calculate the power of the integration of the pluralsymbols, thereby obtaining a power value; a short-time integration pathsearch unit for integrating the power value for the integration timecorresponding to the plural slots and selecting higher power values, thenumber thereof corresponding to the number of the first correlators, inthe magnification order of the power per slot from a larger power perslot to a lower power per slot; a long-time integration path search unitfor integrating the power value for an integration time longer than thatof said short-time integration path search unit by the timecorresponding to plural slots and selecting higher power values, thenumber thereof corresponding to the number of the first correlators, inthe magnification order of power per slot from a larger power value to alower power value; a demodulation path selection unit for selecting areception timing for demodulation from the timings of the power valuesselected in said short-time and long-time integration path search unitsin the order of the magnification of power per slot; a second correlatorfor correlating the reception signal and the spread signal on the basisof the reception timing for demodulation to obtain a second correlationvalue; a detector for detecting the second correlation value andoutputting a detection signal; and a signal composite unit foroutputting a judgment value on the basis of a composite signal which isobtained by transmitting the detection signal to a RAKE/SD (SpaceDiversity) unit through the corresponding path to perform any one ofRAKE synthesis and space diversity (SD) synthesis.
 2. The spreadspectrum communication synchronization acquisition demodulatingapparatus as claimed in claim 1,wherein in said demodulation pathselection unit, the power per slot which corresponds to the timingselected in said short-time integration path search unit and ismultiplied by a weight real number a is compared with the power per slotwhich corresponds to the timing selected in said long-time integrationpath search unit, the same timing and adjacent timings thereto areexcluded, and the reception timings for demodulation are selected in theorder of magnitude.
 3. The spread spectrum communication synchronizationacquisition demodulating apparatus as claimed in claim 1,wherein theweight real number a is set to a large value when a signal interferenceratio (SIR) is large and set to a small value when the signalinterference ratio is small, and in said demodulation path selector, thepower per slot which corresponds to the timing selected in saidshort-time integration path search unit and is multiplied by a weightreal number a is compared with the power per slot which corresponds tothe timing selected in said long-time integration path search unit, thesame timing and adjacent timings thereto are excluded, and the receptiontimings for demodulation are selected in the order of magnitude.
 4. Thespread spectrum communication synchronization acquisition demodulatingapparatus as claimed in claim 1,wherein in said demodulation pathselector a specific predetermined number of timings which are selectedin the magnitude order of the power per slot which corresponds to thetiming selected in said short-time integration path search unit iscompared with a specific predetermined number of timings which areselected in the magnitude order of the power per slot which correspondsto the timing selected in said long-time integration path search unit,and the same timing and adjacent timings thereto are excluded to selectreception timings for demodulation.
 5. The spread spectrum communicationsynchronization acquisition demodulating apparatus as claimed in claim1, wherein in said symbol integrator the correlation value isdemodulated on the basis of the theoretical value of the symbolcorresponding to plural slots whose number exceeds 1 or the judgmentvalue thereof.
 6. The spread spectrum communication synchronizationacquisition demodulating apparatus as claimed in claim 5,wherein in saiddemodulation path selection unit, the power per slot which correspondsto the timing selected in said short-time integration path search unitand is multiplied by a weight real number a is compared with the powerper slot which corresponds to the timing selected in said long-timeintegration path search unit, the same timing and adjacent timingsthereto are excluded, and the reception timings for demodulation areselected in the order of magnitude.
 7. The spread spectrum communicationsynchronization acquisition demodulating apparatus as claimed in claim5,wherein the weight real number a is set to a large value when a signalinterference ratio (SIR) is large and set to a small value when thesignal interference ratio is small, and in said demodulation pathselector, the power per slot which corresponds to the timing selected insaid short-time integration path search unit and is multiplied by aweight real number a is compared with the power per slot whichcorresponds to the timing selected in said long-time integration pathsearch unit, the same timing and adjacent timings thereto are excluded,and the reception timings for demodulation are selected in the order ofmagnitude.
 8. The spread spectrum communication synchronizationacquisition demodulating apparatus as claimed in claim 5, wherein insaid demodulation path selector a specific predetermined number oftimings which are selected in the magnitude order of the power per slotwhich corresponds to the timing selected in said short-time integrationpath search unit is compared with a specific predetermined number oftimings which are selected in the magnitude order of the power per slotwhich corresponds to the timing selected in said long-time integrationpath search unit, and the same timing and adjacent timings thereto areexcluded to select reception timings for demodulation.
 9. The spreadspectrum communication synchronization acquisition demodulatingapparatus as claimed in claim 1,wherein in said symbol integrator thefirst correlation value is demodulated on the basis of the theoreticalvalue of the symbol corresponding to each of plural parts to which aslot is divided, or the judgment value thereof, the demodulation resultis integrated over plural symbols to calculate the power of theintegration of the plural symbols, and then the power values of theplural parts are added to determine the power of the slot concerned. 10.The spread spectrum communication synchronization acquisitiondemodulating apparatus as claimed in claim 9,wherein in saiddemodulation path selection unit, the power per slot which correspondsto the timing selected in said short-time integration path search unitand is multiplied by a weight real number a is compared with the powerper slot which corresponds to the timing selected in said long-timeintegration path search unit, the same timing and adjacent timingsthereto are excluded, and the reception timings for demodulation areselected in the order of magnitude.
 11. The spread spectrumcommunication synchronization acquisition demodulating apparatus asclaimed in claim 9,wherein the weight real number a is set to a largevalue when a signal interference ratio (SIR) is large and set to a smallvalue when the signal interference ratio is small, and in saiddemodulation path selector, the power per slot which corresponds to thetiming selected in said short-time integration path search unit and ismultiplied by a weight real number a is compared with the power per slotwhich corresponds to the timing selected in said long-time integrationpath search unit, the same timing and adjacent timings thereto areexcluded, and the reception timings for demodulation are selected in theorder of magnitude.
 12. The spread spectrum communicationsynchronization acquisition demodulating apparatus as claimed in claim9,wherein in said demodulation path selector a specific predeterminednumber of timings which are selected in the magnitude order of the powerper slot which corresponds to the timing selected in said short-timeintegration path search unit is compared with a specific predeterminednumber of timings which are selected in the magnitude order of the powerper slot which corresponds to the timing selected in said long-timeintegration path search unit, and the same timing and adjacent timingsthereto are excluded to select reception timings for demodulation.
 13. Aspread spectrum communication synchronization acquisition demodulatingapparatus of a spreading code synchronizing circuit provided in a radiocommunication apparatus in which when a spread spectrum signaltransmitted from a transmission side while subjected to spread spectrumprocessing with a spreading code after transmission data are modulatedis subjected to reception demodulation as a reception signal toreproduce the reception data at a reception side, the spread spectrumsignal is subjected to despread spectrum processing with the samespreading code as the transmission side and then demodulated at thereception side, comprising:a signal converter for converting a receivedsignal to a base band signal with a spreading code set as one symbolperiod; a sample hold circuit for sampling the base band signal, holdingthe sampling signal and outputting the sampling signal; a symbolintegrator for demodulating the sampling signal of the basis of thetheoretical value of a symbol when the symbol is known or a judgmentvalue after demodulation for an unknown symbol, integrating thedemodulation result over plural symbols to obtain a symbol integrationvalue; a first correlator for correlating the symbol integration valueand the spread signal based on the spreading code to determine the powerof the correlation and obtain a power value; a short-time integrationpath search unit for adding power values of plural slots and selectinghigher power values in the magnification order of power per slot from alarger power value to a lower power value by the number of the firstcorrelators; a long-time integration path search unit for adding powervalues of plural slots whose number corresponds to the time longer thanthat of the short-time integration path search unit by the timecorresponding to plural slots and selecting higher power values in themagnification order of power per slot from a higher power value to alower power value by the number of the first correlators; a demodulationpath selection unit for selecting a reception timing for demodulationfrom the timings of the power values which are selected by excluding thesame timing and adjacent timings thereto in said short-time andlong-time integration path search units in the magnification order ofpower per slot; a second correlator for correlating the reception signaland the spread signal on the basis of the reception timing fordemodulation to obtain a second correlation value; a detector fordetecting the correlation value and outputting a detection signal; and asignal composite unit for outputting a judgment value on the basis of acomposite signal which is obtained by transmitting the detection signalto a RAKE/SD (Space Diversity) unit through the corresponding path toperform any one of RAKE synthesis and space diversity (SD) synthesis.14. The spread spectrum communication synchronization acquisitiondemodulating apparatus as claimed in claim 13,wherein in saiddemodulation path selection unit, the power per slot which correspondsto the timing selected in said short-time integration path search unitand is multiplied by a weight real number α is compared with the powerper slot which corresponds to the timing selected in said long-timeintegration path search unit, the same timing and adjacent timingsthereto are excluded, and the reception timings for demodulation areselected in the order of magnitude.
 15. The spread spectrumcommunication synchronization acquisition demodulating apparatus asclaimed in claim 13,wherein the weight real number α is set to a largevalue when a signal interference ratio (SIR) is large and set to a smallvalue when the signal interference ratio is small, and in saiddemodulation path selector, the power per slot which corresponds to thetiming selected in said short-time integration path search unit and ismultiplied by a weight real number α is compared with the power per slotwhich corresponds to the timing selected in said long-time integrationpath search unit, the same timing and adjacent timings thereto areexcluded, and the reception timings for demodulation are selected in theorder of magnitude.
 16. The spread spectrum communicationsynchronization acquisition demodulating apparatus as claimed in claim13,wherein in said demodulation path selector a specific predeterminednumber of timings which are selected in the magnitude order of the powerper slot which corresponds to the timing selected in said short-timeintegration path search unit is compared with a specific predeterminednumber of timings which are selected in the magnitude order of the powerper slot which corresponds to the timing selected in said long-timeintegration path search unit, and the same timing and adjacent timingsthereto are excluded to select reception timings for demodulation. 17.The spread spectrum communication synchronization acquisitiondemodulating apparatus as claimed in claim 13,wherein in said symbolintegrator the sampling signal is demodulated on the basis of thetheoretical of the symbol corresponding to the sample value of pluralslots whose number exceeds 1 as the sampling signal, or a judgmentvalue.
 18. The spread spectrum communication synchronization acquisitiondemodulating apparatus as claimed in claim 17,wherein in saiddemodulation path selection unit, the power per slot which correspondsto the timing selected in said short-time integration path search unitand is multiplied by a weight real number α is compared with the powerper slot which corresponds to the timing selected in said long-timeintegration path search unit, the same timing and adjacent timingsthereto are excluded, and the reception timings for demodulation areselected in the order of magnitude.
 19. The spread spectrumcommunication synchronization acquisition demodulating apparatus asclaimed in claim 17, wherein the weight real number α is set to a largevalue when a signal interference ratio (SIR) is large and set to a smallvalue when the signal interference ratio is small, and in saiddemodulation path selector, the power per slot which corresponds to thetiming selected in said short-time integration path search unit and ismultiplied by a weight real number α is compared with the power per slotwhich corresponds to the timing selected in said long-time integrationpath search unit, the same timing and adjacent timings thereto areexcluded, and the reception timings for demodulation are selected in theorder of magnitude.
 20. The spread spectrum communicationsynchronization acquisition demodulating apparatus as claimed in claim17,wherein in said demodulation path selector a specific predeterminednumber of timings which are selected in the magnitude order of the powerper slot which corresponds to the timing selected in said short-timeintegration path search unit is compared with a specific predeterminednumber of timings which are selected in the magnitude order of the powerper slot which corresponds to the timing selected in said long-timeintegration path search unit, and the same timing and adjacent timingsthereto are excluded to select reception timings for demodulation.